a) Field of the Invention
The present invention relates to a semiconductor laser, and more particularly to a semiconductor laser with a light emitting slant plane and without a buried mesa structure.
b) Description of the Related Art
Visible light semiconductor lasers of a 0.6 .mu.m band have recently been regarded as a promising light source capable of improving the performance of optical information processing systems such as point of sales (POS) systems, optical disk drives, and laser printers.
Conventional typical semiconductor lasers use a buried mesa structure. Specifically, an epitaxially laminated structure including an active layer is mesa-etched to define the lateral width of the active layer, and thereafter the mesa structure is buried with material of a low refractive index.
AlGaInP based semiconductor lasers have been expected to be used for visible light semiconductor lasers of the 0.6 .mu.m band. AlGaInP material is required to be grown by metal organic vapor phase epitaxy (MOVPE) or molecular beam epitaxy (MBE) because of the necessity of controlling composition of Al. With these growth methods, it is very difficult to grow a layer containing Al on an underlie layer containing Al because it is difficult to avoid surface oxidation. It is therefore difficult to obtain a refractive index distribution suitable for lateral mode control by burying the mesa structure with material containing Al.
Low cost, low threshold current, and high power are required for visible light semiconductor lasers of the 0.6 .mu.m band. High and stable beam characteristics are also desired, for example, a high kink level, a high quantum efficiency, a low power consumption, far and near field patterns with a single peak, and low beam astigmatism.
If a semiconductor laser can be manufactured by a series of MOVPE processes, an AlGaInP based semiconductor laser can be manufactured at low cost.
Various proposals of forming a laser structure by a series of growth processes have been proposed.